Process for forming passivated film

Abstract

PCT No. PCT/JP92/00160 Sec. 371 Date Jun. 23, 1993 Sec. 102(e) Date Jun. 23, 1993 PCT Filed Feb. 18, 1992 PCT Pub. No. WO92/14858 PCT Pub. Date Sep. 3, 1992.A process for a passivated film which is far reduced in the amount of gas discharge and can desorb an adsorbed gas more readily, which process comprises heating a stainless member with a surface roughness, Rmax, of 1.0 mu m or less in an atmosphere of a mixture comprising oxygen gas and an inert gas and having a dew point of -95 DEG C. or below, an impurity concentration of 10 ppb or less and an oxygen content 5 ppm 25 vol % at 300 DEG to 420 DEG C.

We claim: 
     
       1. A method of forming a passivated film on a stainless steel member having a surface roughness, Rmax, of less than 1.0 micrometers, said method comprising heating said stainless steel member to a temperature within a temperature range of between 300° C. and 420° C. in a mixed gas atmosphere, said mixed gas atmosphere comprising an inert gas and oxygen and having an oxygen concentration within an oxygen concentration range of between 5 ppm and 20 volume percent, a dewpoint temperature of less than -95° C., and an impurity concentration of less than 10 ppb, the stainless steel member being heated for a time sufficient to form the passivated film. 
     
     
       2. The method of claim 1 wherein said dewpoint temperature is less than -110° C. 
     
     
       3. The method of claim 1 wherein said impurity concentration is less than 5 ppb. 
     
     
       4. The method of claim 1 wherein the impurity concentration is less than 1 ppb.